The line chart is one type of chart images, and is mainly composed of horizontal and vertical coordinate axes (including scale values), titles, legends, legend annotations, line data and the like together. The main purpose of analysis on the line chart is to effectively recover all data information in the original image, quantify each data point of the line and correspond to the scales of the analyzed horizontal and vertical coordinate axes at the same time. A viewer finally can view and review relevant data embodied by the line more clearly and accurately through the data recovered and quantified from the line chart.
Generally, the methods for line segment detection are mainly detection based on edge gradients, such as Laplace, Sobel, Canny and the like, or detect the start points, end points and inflection points of line segments by using Huff transform. According to these edges or line segments, approximate directions of the line segments are finally estimated by using complex image processing methods. The traditional edge detection or line segment detection methods are often constrained by many factors such as image noise, definition, etc. In the case of very complicated and mutually staggered lines, it is difficult to segment ideal results using the above methods. Therefore, in prior arts, it usually takes a long time and requires to occupy huge storage space of an electronic device for calculation to segment the lines in the line chart.